From HLG to DLG...Apogee?

Me and a fellow club member here in PA have interest in building a DLG model. He suggested Apogee becuase of the free plans. I have not thought much about the options but free plans are nice and I know my simulator has the Apogee in it (SSS).

He's interested in having a model that will DLG...I don't mind between DLG or HLG but so I think I'd build my plane for both.

36" Apogee is what he's planning materials for. To make it DLG-ready (Apogee is not intended for DLG by-design) he plans to put a layer of 1/64 ply top and bottom and maybe some fiberglass too.

Can anyone recommend what to do to make an Apogee ready for DLG? Or...can anyone recommend a non-composite and easy to build (balsa) DLG plane? Can be built-up or solid balsa like the Apogee.

My fellow pilot asked me to ask you guys about how a single Lipo cell will do in a HLG/DLG and also about what the favored servos are for small, light, HLG/DLGs.

I have used the HES2003 and HES 490 servos for a 42" span rocket glider which was also discus launchable. The centering of the servos is not the best compared to larger servos but these are very light and thin servos and they are adequate for very small models. I would not recomend these servos for a full size discus launch model except maybe for a four wing servo model where each servo only operates a small flap or aileron rather than a full span flaperon.

I was just checking out the Polecat Aeroplane Works site and noticed that he also sells the HES 2003 and HES 490 servos. He has a new accessories page which lists some very DLG componenets. You can buy separate tails, fuselages, wings, and even stab mounts. All top quality high performance competition stuff.

Is there a rule-of-thumb about vertical stabilizer size for a DLG? Any tips? Does length of boom make a difference?

Also, what are some places to buy tailboom material from? CF tube...
tailboom.com has some larger tailbooms.

For a DLG model you want a large vertical fin that extends partially below the boom. Just imitate the current contest models such as Taboo or XP3/4. A longer boom with a smaller fin would act the same as a shorter boom with a larger fin.

The Allegro boom that Tailboom.com sells is the best boom for a full size competition DLG model. For smaller models you want an arrow shaft/ kite spar type boom. Here is a link for those;

This should take you to a page of "G-Force tapered Kite Spars". Most kits and plans will specify or use one of these and you will find these sold by many other distributors as well. This is the most direct and least expensive source that I am aware of. This is my source for micro carbon rods also. I have always ordered by phone. The site has a phone number listed, I did not see any prices or any way to order from the site so I guess you need to call to order. The carbon tube kite spars run about $5 each and small 4' micro carbon rods are about $1 each. They will cut micro carbon rods to any length you like and do not apear to have a minimum order.

Proposed DLG Mods to Wood Apogee

I'm just now planning my wood Apogee DLG building project. I'm not saying I know this will work, but I intend to try the following for DLG reinforcements:

1) I'm going to add carbon spar caps top and bottom to my balsa wings, much like those on the composite molded Apogee. After cutting the outline of the wing and tapering the blank, I hope to sand a shallow groove (Ron Gauthier's idea) at the airfoil high point, laminate a tapered carbon tow ribbon into the groove and fill the groove with lightweight sanding sealer, all before sanding the airfoil using Mark's recommended method from the Apogee site.

2) I plan to put similar carbon tow tape reinforcements on the outside of both sides and bottom of the pod, from nose to boom.

4) Oh yea! And I'm going to use a cruciform tail, sized to match the effective horizontal area of the v-tail, and enlarging the effective vertical area proportionally to increase the C-sub-v to 0.04, like the SuperGee.

Otherwise, it'll be a stock wood Apogee.

One more thing I'm considering: You need ~3/8 thick, 4-4.5 lb. wing stock, but I have only 5 lb., 1/4". I might try tapering two pieces in advance, then hollowing the inside faces somewhat (following the anticipated airfoil contour) before laminating them with model airplane cement (sandable). I'd hope this slightly hollowed wing would compensate for the 5 lb. wood.

(Mark Drela: I'd very much appreciate your comments on the above plan. Thanks.--MT)

Thermals,

Marc

Last edited by marctrudeau; May 09, 2004 at 11:22 AM.
Reason: pilot error

Thanks again guys! Rcgroups is great!
So what are the surface areas of the fin/stab you're making, marc? One thing I read was that by thinning the airfoil 10-15% with 5lb wood it makes up for the difference in weight. I see yours will have to be thinner because of how yours is 1/4" thick rather than 3/8" thick.
The guy I'm figuring this out with is finding a place to get 4lb balsa.
Anybody have anything else to add? I've still got some questions unanswered from my first post in this thread...
~John

Images

D-box is very key in gettng a balsa DLG scratch built working. Either solid or hollow will work. I use hollow with CF reinforcement at the spar and a hardwood dowel at the LE. I've used CF tube on my LE but it is heavier than you need and overkill strength wise. The killer on thes wings is tortional stiffness. If your wing isn't stiff tortionally it will flutter on launch and explode. The 2nd thing you need is enough strength at the peg to handle the G-forces of a full DLG throw. Get those two down and get a boom stiff enough and you'll be damn close.

The Avia booms are nice and light, but depending on the size of your plane may be too weak. If you're sticking to Mosquito class they're great. Above that I like the Skyshark series. They're heavier but a LOT stronger. Oh and if you get up to 1.5 meter span go directly to Rick Walba (www.tailboom.com) and get his DLG boom. It's the best.

I believe Mosquito limits are .75 meters (29in) for the wingspan. But to be honest, I don't know anyone who holds contests in this class.

There are many posts about tail volume (do a search), but I tend to go for about 10% of main wing area for the horizontal stab (full flying) and close to the same area (but generally less) for the vertical. There are many qualified experts on this topic. Poke through past posts for the gems of knowledge or wing it and see how it works.

With a full flying stab and tape hinges for the elevator, it's simple to make interchangeable parts to test the impact on your airframe. I use 3/32 balsa and waterborne polyurethane to save weight. No covering. A little glass reinforcing at the boom mount and you are good to go. I've never broken a tail yet.